Safety device

ABSTRACT

A personal safety device ( 10 ) adapted for longitudinal movement relative to an elongate support element ( 50 ) comprises a body ( 11 ) having a bore ( 12 ) for receiving the element ( 50 ), a slipper ( 20 ) mounted on the body ( 11 ) the slipper ( 20 ) having a surface ( 21 ) oriented substantially parallel to the longitudinal axis of said bore ( 12 ), and connector ( 30 ) connected to the slipper ( 20 ) and being adapted at its other end ( 31 ) for connection to a personal safety harness. Slipper ( 20 ) is movable between first and second positions in response to sudden loading of the connector ( 30 ). In the first position, surface ( 21 ) allows free passage element ( 50 ) through the bore ( 12 ). When slipper ( 20 ) is in the second position, surface ( 21 ) clamps element ( 50 ) firmly to body ( 11 ).

The present invention relates to a safety device and, in particular, toa versatile personnel safety device for reducing the risk of injury topersonnel engaged in work in elevated or vulnerable positions, such ashigh buildings or the deck of a boat or ship.

Personnel safety appliances, such as vertical fall arrest devices, arean important accessory for personnel working in situations where a fallis potentially life-threatening, since they enable the hazard of a fallto be minimised. Vertical fall arrest systems are known which employ asafety line such as a flexible cable for engagement, in a fall arrestsituation, by a fall arrest device. Such systems require intermediatesupport brackets to restrain the cable from buffeting against the fixedstructure while under wind loading. These systems therefore present apractical problem of enabling the fall arrest device (and the user) tobypass the support brackets without increasing the fall hazard.

Certain known designs attempt to overcome this bypass problem by using amanually operated bracket lock. This requires the user to open and closethe bracket when he traverses it. Other known designs require that theuser should lean out from the normal climb/descend posture and pull thecable away from the bracket in order to move the fall arrest device pastthe bracket position. Both of these methods add significantly to thedifficulty of the climb, are more tiring and hence possibly increase thefall hazard.

Some very tall structures, such as telecommunication pylons, masts etc.,have a number of separate spans of elongate safety element around thestructure. This is due to the fact that ladder placement is often alonga number of different climbing axes. Such structures may thereforerequire the detachment and re-attachment of the safety device at anypoint during the climb or descent, and the ease with which this can beachieved is an important factor in determining the overall safety of themanoeuvre.

One of the drawbacks of the above-described arrangement, in which thestructure includes a number of separate spans of elongate safety elementaround its periphery, is that personnel must detach themselves from onevertical span and undertake a horizontal traverse, perhaps unsecured,before attaching themselves to the next vertical span.

Another disadvantage of known vertical fall arrest devices is that theytend to be uni-directional with regard to their fall arrest capability.For example, where the fall arrest device relies on a cam locking actionfor gripping the cable, the device needs to be installed on the cable inthe correct orientation for effective operation. If it is installed thewrong way up, the cam cannot grip the cable when the device isdescending the cable. Hence, it is ineffective as a fall arrest aid.

To overcome this drawback, the device can be configured to preventincorrect installation. However, this usually increases its complexityand, inevitably, its weight and cost.

Another drawback of unidirectional cam-locking devices is that they arenot ideal for use by personnel working on the apex of a roof, or similarstructures where the surface slopes in more than one direction. In suchcircumstances, a common safety cable may be provided which crosses theroof apex and spans both slopes either side of it. If a workman wishesto ascend one side and descend the other, he must re-orient his fallarrest device at the point where the roof slope changes direction. Thisis analogous to the situation described above in which intermediatehorizontal traverses are executed between different vertical spans ofsafety cable. The workman is at his most vulnerable at the change-overpoint and it would be preferable if such circumstances could be avoided.

Above all, it is inconvenient to the workman to have to detach andreattach a safety device every time a change in orientation occurs. Suchinconvenience is likely to lead to the situation in which the workmantakes risks by declining to re-attach his fall arrest equipment to thesafety cable for brief periods, thereby adding to the fall hazard.

Cable-mounted fall arrest devices have been proposed which attempt toaddress this problem by using double cams. One cam is mounted toactivate in a fall arrest situation when the device is travelling alongthe cable in a first direction, whilst the second cam is mounted in theopposite sense and activates in a fall arrest situation when the deviceis travelling in the opposite direction.

One drawback of these proposed double cam devices is that they are bulkyand hence heavy to wear. Their bulk also means that they can onlynegotiate larger radius curves on the suspended cable, with the resultthat their applicability is limited. In addition, they can beinconvenient to handle during installation on the cable because the camshave to be manipulated into a position which allows passage of the cableinto the mechanism.

It is therefore an object of the present invention to provide aversatile hands-free personnel safety device for reducing the risk ofinjury to personnel engaged in work in elevated or vulnerable positions,which is adapted to travel along a continuous span of elongate safetyline regardless of the orientation of the safety line. It also an objectof the present invention to provide a versatile personnel safety devicehaving bi-directional fall arrest capability. It is a still furtherobject of the present invention to provide a versatile personnel safetydevice which requires minimal manipulation on the part of the user tonegotiate intermediate support brackets and/or changes in orientation ofa safety line to which the device is attached in use.

The invention is a personnel safety device adapted to be installed inuse on a fixed elongate support element in a manner which allowstranslational movement of the device along said elongate supportelement, said device comprising a body member having a bore forreceiving said elongate support element, slipper means mounted on saidbody member said slipper means having a control surface orientedsubstantially parallel to the longitudinal axis of said bore, andconnecting means connected at one end to said slipper means and beingadapted at its other end for connection to a personnel safety harness,said slipper means being movable in response to sudden loading of theconnecting means between a first position in which the control surfaceallows free passage of the elongate support element through the bore anda second position in which the control surface grips the elongatesupport element firmly relative to the body member, in which saidslipper means maintains the control surface in its orientationsubstantially parallel to the longitudinal axis of said bore throughoutmovement of the slipper means between said first and second positions,and characterised in that the body member is provided with ramp surfacesengageable by the slipper means, said ramp surfaces being adapted toeffect movement of the slipper means between its first and secondpositions.

When the device is subjected to rapid acceleration and/or suddenmovements, for example in the event of a fall by a workman connected tothe device through a lanyard, this is experienced initially by theconnecting means which is connected to the slipper means. The slippermeans moves in a direction to follow the sudden applied load, suchmovement occurring fractionally before the body member is able to move.As a result, the slipper means moves from its first position, in whichthe control surface allows free passage of the elongate support elementthrough the bore of the body member, to its second position, in whichthe control surface grips the elongate support element firmly relativeto the body member. The device thus locks on to the elongate supportelement and remains in position until such time as the tensile loadingis intentionally removed.

If the workman is incapacitated as a result of the fall, he will remainsuspended by his safety harness until he is rescued.

Because the slipper means moves in a manner which maintains the controlsurface in an orientation substantially parallel to the longitudinalaxis of the bore of the body member, the device has bi-directional fallarrest capability.

Preferably, the slipper means is mounted in the bore, with theconnecting means protruding through an aperture in the body member. Innormal use, the slipper means lies in a neutral position at the base ofthe ramp means, the control surface allowing free passage of theelongate support element through the bore of the body member. However,in a fall arrest situation, the slipper means moves along the ramp meansto an active position in which the control surface grips the elongatesupport element and holds the device fast relative thereto.

In its neutral condition, the slipper means may be urged into lightcontact with the elongate support element to assist in smooth passage ofthe device along the element. For example, compression springs may beused to urge the slipper means radially inwardly towards the centre ofthe bore. However, it is important to note that, whatever resilientmeans are used bring about this light contact with the elongate supportelement, the return force is easily overcome and the resilient means ontheir own are incapable of locking the device onto the elongate supportelement in a fall arrest situation.

The safety device is part of a fall arrest system which comprises endanchors and intermediate brackets for supporting the elongate element.The device is able to negotiate the intermediate brackets without userintervention, thereby minimising the risks associated with detachment ofthe line to transfer between adjacent spans of support element.

Preferably, the body member of the device has a slot extending along itslength and radially outwardly from the bore to the exterior of said bodymember for allowing passage of the device past intermediate brackets forthe elongate support element. Most preferably, the longitudinal slot isprovided in the body member at a circumferential orientation relative tothe slipper means other than 180°±50°. This means that, should the fallarrest device ever be deployed in a fall arrest situation, the elongatesupport element does not become compressed into the longitudinal slot bythe control surface of the slipper means.

Alternatively, the body member may be tubular with no longitudinal slot.To enable this variant to traverse intermediate brackets supporting theelongate support element, these brackets are provided with an aperturedimensioned to accommodate the body member of the device and have a slotto allow passage of the connecting means past the support point.

The invention will now be described by way of example only withreference to the drawings, in which:

FIG. 1 is a perspective view of a personnel safety device in accordancewith a preferred embodiment of the present invention;

FIG. 2 is a side sectional view of the device of FIG. 1;

FIG. 3 is a sectional view from above of the device shown in FIG. 2;

FIG. 4 is a sectional end elevation of the device depicted in FIGS. 2and 3;

FIG. 5 is a view similar to FIG. 2 showing the device in acable-gripping position:

FIG. 6 is a sectional view from above of the device in itscable-gripping position as shown in FIG. 5;

FIG. 7 is a sectional end view of the device in its cable-grippingposition as shown in FIGS. 5 and 6;

Referring now to FIG. 1, a personnel safety device 10 in accordance witha preferred embodiment of the present invention comprises a body member11 fashioned out of a suitable material such as stainless steel. Thebody member 11 has a central bore 12 dimensioned to receive an elongatesupport element such as a multi-stranded safety cable. Typically for afall arrest system, the cable will have an external diameter of 8 mm andthe bore 12 of the body member will have a diameter of 12 mm. Bodymember 11 may have special formations at both of its ends 13, 14 toassist in negotiating intermediate support brackets in substantiallyhands-free fashion, in a manner to be described in more detail below. Aconnecting member 30 protrudes from one side of the body member 11 andincludes a connecting eye 31 adapted to receive a karabiner or similardevice for attaching a personnel safety harness to the device 10 bymeans of a lanyard.

Turning now to FIGS. 2 to 4, the device 10 is shown installed on asafety cable 50. Cable 50 is attached at remote locations by end anchorsto a fixed structure (not shown) and will be supported at intervalsalong its length by intermediate support brackets. As best seen in FIG.4, body member 11 is provided with a longitudinal slot 15 which extendsradially from the bore 12 to the exterior of the body member 11 for itsentire length between ends 13, 14. The slot 15 is dimensioned to receiveand pass a limb of an intermediate support bracket for the cable 50 sothat the device 10 can pass along the entire cable length withouthindrance. The limb may be in the form of a flat web lying in a planeparallel to the longitudinal axis of the cable 50, said web providingthe connection between the cable-supporting part of the bracket and thefixing plate or similar means by which it is attached to a fixedstructure. At the ends 13, 14 of the body member 11, the material of thebody member 11 may be cut away to form a substantially V-shaped slotwhich assists in aligning the device with intermediate support bracketsfor ease of passage in a hands-free manner.

As best seen in FIGS. 2 and 4, the connecting member 30 passes throughan aperture 16 in one side of the body member 11 of the device 10 and isattached to a slipper element 20. The attachment of the connectingmember 30 to the slipper element 20 may be effected by any suitablemeans, such as a series of bolts passing through an upper flange 32 ofthe connecting member 30 and screwed into threaded holes (not shown) inthe underside of the slipper element 20.

As best seen in FIG. 4, slipper element 20 has a control surface 21which has a concavity that is complementary to the outer circumferenceof the cable 50.

In FIGS. 2 to 4, the slipper element 20 is shown seated in a neutralposition near the mid-point of the body member 11. The slipper element20 need not make any physical contact with the cable 50 in thiscondition, not even light contact.

The central portion of the body member 11 is provided with a pair oframp surfaces 17, 18 which are adapted to be engaged by formations 27,28 provided on the sides of the slipper element 20. If the device 10 isthen subjected to rapid acceleration and/or sudden movement in adirection having a component along the longitudinal axis of the cable50, for example in the event of a fall by a workman connected to theconnecting eye 31 through a lanyard, the connecting member 30 transmitsthis sudden movement to the slipper element 20. Slipper element 20 isthus caused to move in a direction that follows the sudden applied load(here indicated by arrow A), along ramp surface 17, to the positionshown in FIGS. 4 to 6.

As best seen in FIG. 6, the control surface 21 of the slipper element 20is forced into firm engagement with the exterior of the cable 50 whichbecomes gripped between the slipper element 20 and the bore 12 of thebody member 11. The device 10 is held fast on the cable 50 and willremain in position until removal of the tensile load which causedactivation of the slipper element 20 to its cable-gripping state.

It will be readily apparent to persons skilled in the art that suddenmovement in the sense opposite the direction indicated by arrow A wouldresult in the slipper element 20 being moved up ramp surface 18 instead.Nevertheless, an equivalent cable-gripping state is achieved. Thus, thedevice 10 is truly bi-directional in its fall arrest capability.Moreover, the cable-gripping capability is effective regardless of theinclination of the cable. All that is required to achieve cable grippingis a sudden movement in a direction having a component along thelongitudinal axis of the cable 50, such that the inertia of the bodymember 11 relative to the slipper element 20 causes the slipper element20 to move along one of the ramp surfaces 17, 18.

Using the device of the present invention, it is therefore possible forthe installer of a height safety system to use a single elongate supportelement in substantially horizontal or substantially verticalorientations, and orientations in between, in the same installation andwithout the need for separate spans for each change in orientation.

Although the invention has been particularly described above withreference to specific embodiments, it will be understood by personsskilled in the art that these are merely illustrative and thatvariations are possible without departing from the scope of the claimswhich follow.

What is claimed is:
 1. A personnel safety device (10) adapted to beinstalled in use on a fixed elongate support element (50) in a mannerwhich allows translational movement of the device (10) along saidelongate support element (50), said device (10) comprising a body member(11) having a bore (12) for receiving said elongate support element(50), a slipper (20) mounted on said body member (11), said slipper (20)having a control surface (21) oriented substantially parallel to alongitudinal axis of said bore (12), and connecting means (30) connectedat one end to said slipper (20) and being adapted at the other end forconnection to a personnel safety harness, said slipper (20) beingmovable in response to sudden loading of the connecting means (30)between a first position in which the control surface (21) allows freepassage of the elongate support element (50) through the bore (12) and asecond position in which the control surface (21) grips the elongatesupport element (50) firmly relative to the body member (11), in whichsaid slipper (20) maintains the control surface (21) in the orientationsubstantially parallel to the longitudinal axis of said bore (12)throughout movement of the slipper (20) between said first and secondpositions and characterized in that the body member is provided withramp surfaces (17, 18) engageable by the slipper (20), said rampsurfaces (17, 18) being adapted to effect movement of the slipper (20)between the first and second positions.
 2. The personnel safety device(10) as claimed in claim 1 wherein the slipper (20) is mounted in thebore (12) and the connecting means (30) protrudes through an aperture(16) in the body member (11).
 3. The personnel safety device (10) asclaimed in claim 1 wherein the body member (11) has a slot (15)extending along its length and radially outwardly from the bore (12) tothe exterior of the body member (11).
 4. The personnel safety device(10) as claimed in claim 3 wherein the longitudinal slot (15) isprovided in the body member (11) at a circumferential orientationrelative to the slipper (20) other than 180°±5°.
 5. The personnel safetydevice (10) as claimed in claim 1 wherein the body member (11) istubular and includes first and second spaced apart opposite axial ends(13, 14) and a longitudinal slot (15) extending a distance between butnot up to said first and second axial ends (13, 14).
 6. A height safetysystem incorporating a fixed elongate support element (50) and at leastone personnel safety device (10) installed on the fixed elongate supportelement (50) in a manner which allows translational movement of thedevice (10) along said elongate support element (50), said device (10)comprising a body member (11) having a bore (12) for receiving saidelongate support element (50), a slipper (20) mounted on said bodymember (11), said slipper (20) having a control surface (21) orientedsubstantially parallel to a longitudinal axis of said bore (12), andconnecting means (30) connected at one end to said slipper (20) andbeing adapted at the other end for connection to a personnel safetyharness, said slipper (20) being movable in response to sudden loadingof the connecting means (30) between a first position in which thecontrol surface (21) allows free passage of the elongate support element(50) through the bore (12) and a second position in which the control(21) grips the elongate support element (50) firmly relative to the bodymember (11), in which said slipper (20) maintains the control surface inthe orientation substantially parallel to the longitudinal axis of saidbore (12) throughout movement of the slipper (20) between said first andsecond position and characterized in that the body member (11) isprovided with ramp surfaces (17, 18) engageable by the slipper (20),said ramp surface (17, 18) being adapted to effect movement of theslipper (20) between the first and second positions.
 7. A personnelsafety device for location on a fixed elongate support element, thedevice surrounding the elongate support element and being movablerelative to the elongate support element when located on the elongatesupport element, the device comprising: a body member extending along alongitudinal axis and defining a bore for receiving the elongate supportelement, a slipper mounted on the body member, the slipper having acontrol surface located parallel to the longitudinal axis, and aconnecting means connected at one end to the slipper and being adaptedat the other end for connection to a personnel safety harness, theslipper being movable, in response to a sudden force exceeding apredetermined force applied to the connecting means, between a firstposition in which the control surface does not engage the elongatesupport element and the elongate support element moves freely throughthe bore and a second position in which the control surface grips theelongate support element firmly against movement relative to the bodymember, the control surface remaining in the location parallel to thelongitudinal axis throughout movement of the slipper between the firstand second positions, the body member including ramp surfaces which aresurfaces inclined relative to the longitudinal axis, the slipper slidingon the ramp surfaces between the first and second positions.